When measuring RF power, it is necessary to define the physical point in the system at which the measurement is made. This is because the transmission of RF power, whether through space, waveguide, or coaxial transmission lines is subject to loss. RF power measured in one place is only an accurate measure of RF power at another place to the extent that the transmission losses are known.
For this reason, equipment for measuring RF power often separates the RF power sensing element from the measuring equipment, so that the sensing element can be remote. The advantage of this arrangement is that whilst the full RF power measurement equipment may be large, the power sensing element can be made small and connected directly to the unit under test.
FIG. 1 shows a known example of this technique.
When generating RF power, it is also necessary to define the physical point in the system at which the output power is specified. As stated before, the transmission of RF power is subject to loss. RF power generated at one place is only an accurate measure of RF power generated at another place to the extent that the transmission losses are known.
For this reason, equipment for generating known RF power is sometimes used with a remote RF power sensing element, which may be connected to a separate means of power measurement, or may form part of a feedback loop which controls the RF power generation equipment. Such a system provides a signal source whose RF power at a defined point is determined by the accuracy of the remote sensor and the coupling device. The advantage is that whilst the full RF power generation equipment may be large, the power sensing element and coupling device can be made small, and connected directly to the unit under test.
FIG. 2 shows a known example of this technique.
Radio communication equipment often has either a single RF connector for transmission and reception, or one RF connector for transmission and another for reception. When characterising such equipment it is required both to measure the RF power transmitted by the unit under test, and to set the RF power received by the unit under test. It is usual to specify both powers at the RF connector or connectors of the unit under test.